Redundant power distribution

ABSTRACT

A fault-tolerant power distribution architecture is described in which electrical power-consuming modules are connected in rows via individual busses in a first set of busses connected to individual power supplies in a first set of power supplies, and are also connected in columns via successive busses in successive sets of busses connected to power supplies in successive sets of power supplies such that each module receives power from a unique combination of a first bus and a first power supply and a successive bus and successive power supply.

TECHNICAL FIELD

This invention relates to the art of redundantly providing power toelectronic modules in a process control system wherein the power isderived from one or more current mains, via a plurality of powerdistribution sources in a fault-tolerant scheme.

BACKGROUND ART

Direct current converters or DC power supplies are conventionallypowered from one or two sources, usually either regular mains or factorypower. In a single-source system, of course, each module powered by thepower supply receives power from a single source. The powered modulesare simply connected in parallel via a single power bus system. In aconventional "fail-safe" or double-source system, each of the poweredmodules is connected in parallel along a first bus to a first source andalso along a redundant second bus to a second source; each modulereceives power from either of the two sources. This technique providesprotection in the case of a single supply failure (or supply sourcefailure when the supplies are fed power from separate sources) and inthe case of any individual module presenting an open circuit to thesupply bus. These are the more common failure mechanisms; the prior artmethods usually work well as simple redundant supply techniques.

However, when a module fails such that a short circuit is presented tothe bus or when a bus or power supply fails such that the short circuitis presented to all modules along the bus, the reliability of theredundant supplies fails and continued supply of power to the modules islost. Failure of both the first and second busses supplying a given setof modules results in failure of all the modules in that set. Thepresent invention is directed to solving these problems.

The availability of power to operate the equipment in a process controlsystem, like many other systems, is dependent on the availability ofpower. Availability is a function of reliability andmean-time-to-repair. Often, when a module or power supply fails it isdifficult to repair/replace it without turning off power to the entiresystem or at least disconnecting a group of modules. It is preferable torestore the power supply with minimal loss of power to the system orsubsystem. This is called `hot` repair or replacement, and isfacilitated by the present invention. `Hot` repair was difficult orimpossible to safely achieve with many prior art redundant power supplytechniques. The present invention facilitates rapid repair by enablingreplacement of failed modules or power supply units without disruptingthe entire system or subsystem in which the power failure occured.

Prior art redundant mains (also called `factory`) power frequentlyconsisted of merely switching between two sources of AC power. Thismethod may involve a `dropout` of AC power, which if of sufficientlylong duration is harmful to solid-state systems and causes loss ofmemory in power-dependent memory devices. An embodiment of the presentinvention extends the redundant technique to a supply architecture inwhich line voltage dropout is minimized or eliminated, and incombination with the power distribution technique disclosed providesfault tolerance which provides both fully redundant power and powerdistribution using the same set of modules required for non-redundantpower.

DISCLOSURE OF THE INVENTION

In the present invention, the powered modules are electrically arrangedsuch as may be visualized most easily by a rectangular array of unionand intersect points, or a matrix of rows and columns such that each rowrepresents a group of modules receiving power from a first bus, and eachcolumn represents a group of modules receiving power from a second bus.All row power busses comprise the first set of busses and all columnpower busses comprise the second or successive set of busses. Each busis connected to a separate power supply. Each module in the entirecollection of modules receives power in a fault tolerant manner from anexclusive combination of two different power supplies including a firstbus and a successive bus. No two modules are dependent on power from thesame combination of power supplies. Failure of any two separate suppliescan only result in loss of power to a single module. This fault-toleranttechnique prevents a short circuit in any individual module frominterrupting power to other modules, and is accomplished withoutnecessitating additional power supplies or converters. Extra redundancyis provided by supplying the `row` power supplies with power from afirst main source and the `column` power supplies from a second mainsource.

Each module may optionally include power conversion when required, andmay be supplied with either AC or DC source power. That is, either orboth AC and DC power may be supplied to the power supplies or to thepower-consuming modules. A failure of either the AC or DC sources doesnot result in failure of the power-consuming module due to power loss.This permits maximum voltage and current flexibility in a system ofmultiple modules and/or subsystems including multiple modules.

It is not intended that the scope of the present invention be limited toa rectangular matrix connection scheme, but rather includesconfigurations of power distribution wherein multiple power suppliesprovide power to a plurality of powered modules wherein each poweredmodule receives power from a unique combination of two power supplies.

It is therefore an objective of the present invention to provideimproved redundance in multiple sources of power to a plurality ofcircuit modules. Another object is to provide fault-tolerant supply ofpower to a plurality of circuit modules.

An advantage of the present invention is that short-circuits inindividual modules, busses, or supplies does not cause loss of power tothe remaining modules. Another advantage is that `hot` replacement orrepair of defective power supplies is facilitated.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Numerous features of the invention disclosed herein will be apparentupon examination of the drawing figures forming a part hereof. In allviews, like reference characters indicate corresponding parts:

FIG. 1 is a simplified block diagram illustrating the present inventionin simple form as a matrix;

FIG. 2 is a simplified block diagram illustrating the invention in analternate embodiment; and

FIG. 3 is a simplified block diagram of the technique common in theprior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be described in simple form, omitting such extracircuit elements as are ordinarily used for transient protection,overload protection, load switching, and electromagnetic interference,in order to improve understanding of the invention. While such circuitimprovements are not described, their omission is not intended toexclude systems incorporating these improvements from the scope of theclaims.

The advantages of the present invention 10 shown in FIG. 1 are best seenin comparison with the prior art. Turning first to the prior art, FIG. 3shows a technique common in the system power supply art for redundantsupply of power to multiple modules 11-35. In this architecture, eachmodule is a row group (e.g. 11-15, 16-20, etc.) receives power from afirst power supply in a set of first supplies 101 through 105 along afirst bus in a set of first busses 51-55 and also from a second supplyin a second set of supples 201 through 205 along a second bus in a setof second busses 61-65. An open circuit failure in a module 11-35 won'tresult in a failure in another module 11-35. A short circuit in anindividual module 11-35 may result in a short circuit along an entirebus. For example a short circuit in module 13 can result in loss ofpower to all modules in the group of modules 11 through 15 by shortingboth busses 51 and 61. Such short circuits may be caused by componentfailure, failure of protective measures, physical or environmentaldamage, or catastrophic events. The failure of a power supply through anoutput short circuit can short circuit the power inputs to all of themodules to which it supplies power. A short circuit along a bus or in apower supply can result in a loss of power to all modules powered by agiven bus or power supply, including loss of power from the redundantbus. Again, for example, if power supply 201 or bus 61 isshort-circuited, modules 11 through 15 all lose power. If there is aloss of power failure on both bus 53 and on bus 63, all modules in thegroup of modules 21-25 lose power. Troubleshooting may be impaired ordelayed because the failure location may not be apparent and may bedifficult to trace under power-on conditions.

In the technique of the present invention 10, FIG. 1, a similar group ofmodules 11-35 receives power from a first power supply 101 in a firstset of power supplies 101-105 along a first bus 51 in a set of firstbusses 51-55. Module 11 also receives power from another power supply301 in a set of second power supplies 301-305 along another bus 71 whichis a bus element of a second set of busses 71-75. The dotted lines, asbetween modules 14 and 15 and between power sources 104 and 105,indicate that the architecture may be expanded to include anyappropriate additional rows and columns. Note that it is not essentialfor the modules to be connected to orderly arrangements of row andcolumn busses, as the modules may be connected to the busses in randomorder. Each of the modules 11-35 receives its power from either or bothof a unique set of two power sources. For the orderly matrix exampleillustrated, module 13 receives power from either or both power sources101 and 303.

Troubleshooting is facilitated in that any loss of power along a singlerow or column bus does not interrupt power to any given module. Thus,power supplies may be exchanged without loss of power to any module whena single bus/power supply failure occurs. `Hot` exchange enables rapidtroubleshooting and repair. Similarly, with loss of power along any twobus/powers supply paths results in loss of power to a single moduleonly. `Hot` replacement of power supplies is still available, andtroubleshooting along a bus is made possible because all modules alongany row or column continue to receive power from two sources except theaffected row or column. Identification of the module sustaining thedouble-fault power loss, normally a traceable alarm function, givesimmediate recognition of the failed bus/power row and columncombination. Replacement or repair of either failed power supply or busrestores power immediately, and replacement or repair of the otherfailed power supply or bus restores redundant, fault-tolerant power.

An extension of this power source technique is shown in FIG. 2, whereeach of a plurality of power sources 101-105 and 301-305 are shown forillustrative purposes. Each of the power supplies receives its powerfrom a unique combination of major power such as two separate sources ofmains or factory power. The power sources may be either AC or DC,including both mains and factory power. This means that sources of powerto the power supplies (or to the power-consuming modules) may be OR'edfor redundancy. For example, power supply 101 receives its power fromeither or both power sources 401 and 501. Since each set of powersources receives its power from a separate factory power source ormains, loss of factory power from either mains will not result in powerfailure to a single power source 101. Referring again to FIG. 1, eachmodule 11-35 is supplied by a unique combination of power supplies101-105, 301-305, and with each power supply provided with a separatepower source 401, 402; 501, 502 (FIG. 2) multiply redundant andfault-tolerant power is always available to each module 11-35 except formassive, multiple source failures or interruptions.

The foregoing examples are provided for illustrative purposes only andare not intended to limit the following appended claims solely to thespecific examples given.

It is claimed:
 1. Redundant power distribution apparatus for use in anorganization of electrical power consuming modules, comprising:(a) atleast one power bus in a set of power busses; (b) at least one powersupply in a set of power supplies, each of which power supplies isconnected to a respective power bus from the set of power busses; (c) aplurality of power consuming modules forming a group of modules, eachbeing connected in turn to a power bus; (d) additional individual powersupplies; (e) additional individual power busses, each of saidadditional power busses being connected in turn to one of saidadditional power supplies;wherein each of said power consuming modulesis connected to and receives power only from a unique combination of: apower supply in the set of power supplies and a power bus in the set ofpower busses, and one of said additional power busses which is connectedto one of said additional power supplies.
 2. Power distributionapparatus for use in an organization of electrical power consumingmodules enabling `hot` replacement of defective modules, comprising:(a)at least one power bus in a first set of power busses; (b) at least onepower supply in a first set of power supplies, each of which first powersupplies is connected to a related power bus from the first set of powerbusses; (c) at least one power bus in a second set of power busses; (d)at least one power supply in a second set of power supplies, each ofwhich second power supplies is connected to a related power bus from thesecond set of power busses; (e) a plurality of power consuming modulesforming a group of modules, each being connected in turn to a firstpower bus and a second power bus;wherein each of said power consumingmodules is connected to and receives power from a only power supply inthe first set of power supplies via a related power bus in the first setof power busses and a unique combination of one of said second powersupplies via a related second power bus in the second set of powerbusses.
 3. Apparatus as in claim 2 wherein said individual powerconsuming modules are connected in a matrix configuration to receivepower only from a unique combination of a power supply in the first setof power supplies via a related power bus in the first set of powerbusses and a power supply in the second set of power supplies via arelated power bus in the second set of power busses.
 4. Apparatus as inclaim 2 wherein at least one of said power supplies provides alternatingcurrent.
 5. Apparatus as in claim 2 wherein at least one of said powersupplies provides direct current.
 6. Apparatus as in claim 4 furtherincluding power conversion means on-board within each of said modules.7. Apparatus as in claim 6 further including power regulation meanson-board within each of said power consuming modules.
 8. Apparatus forproviding redundant current from first and second mains power sources toa plurality of power supplies, comprising:(a) first means for derivingpower from said first current mains; (b) successive first means forderiving power from said first current mains; (c) second means forderiving power from said second current mains; (d) successive secondmeans for deriving power from said second current mains; and (e) meansfor connecting each of said power supplies to a unique combination ofsaid means for deriving power from said first current mains and saidmeans for deriving power from said second current mains.
 9. Apparatus asin claim 8 wherein at least one of said power sources is a directcurrent source.
 10. Apparatus as in claim 8 wherein at least one of saidpower sources is an alternating current source.
 11. Apparatus as inclaim 8 wherein said means for deriving power from a first current meansproduces alternating current and said means for deriving power from asuccessive current means produces alternating current.
 12. Apparatus asin claim 8 wherein said means for deriving power from a first currentmeans produces direct current and said means for deriving power from asuccessive current means produces direct current.
 13. The method fordistributing redundant power to successive levels of power sources,comprising:(a) providing mains power derived from a first mains to afirst group of power supplies; (b) providing mains power derived from asecond mains to a second group of power supplies; (c) distributing powerfrom said first goup of power supplies to a plurality of power consumingmodules via successive first busses; (d) distributing power from saidsecond group of power supplies to said power consuming modules viasuccessive second busses;wherein individual said power consuming modulesreceive power only from a unique combination of a first power bus and asecond power bus.
 14. The method of claim 13 wherein individual powerconsuming modules receive power from a unique combination of a firstpower bus and a second power bus in a matrix arrangement.
 15. The methodof claim 13 wherein the mains power distributed is alternating current.16. The method of claim 14 wherein the power distributed is alternatingcurrent.